463 research outputs found
Spin orbit alignment for KELT-7b and HAT-P-56b via Doppler tomography with TRES
We present Doppler tomographic analyses for the spectroscopic transits of
KELT-7b and HAT-P-56b, two hot-Jupiters orbiting rapidly rotating F-dwarf host
stars. These include analyses of archival TRES observations for KELT-7b, and a
new TRES transit observation of HAT-P-56b. We report spin-orbit aligned
geometries for KELT-7b (2.7 +/- 0.6 deg) and HAT-P-56b (8 +/- 2 deg). The host
stars KELT-7 and HAT-P-56 are among some of the most rapidly rotating
planet-hosting stars known. We examine the tidal re-alignment model for the
evolution of the spin-orbit angle in the context of the spin rates of these
stars. We find no evidence that the rotation rates of KELT-7 and HAT-P-56 have
been modified by star-planet tidal interactions, suggesting that the spin-orbit
angle of systems around these hot stars may represent their primordial
configuration. In fact, KELT-7 and HAT-P-56 are two of three systems in
super-synchronous, spin-orbit aligned states, where the rotation periods of the
host stars are faster than the orbital periods of the planets.Comment: 9 pages, accepted for publication in MNRA
Multiwavelength transit observations of the candidate disintegrating planetesimals orbiting WD 1145+017
We present multiwavelength, ground-based follow-up photometry of the white dwarf WD 1145+017, which has recently been suggested to be orbited by up to six or more short-period, low-mass, disintegrating planetesimals. We detect nine significant dips in flux of between 10% and 30% of the stellar flux in our ~32 hr of photometry, suggesting that WD 1145+017 is indeed being orbited by multiple, short-period objects. Through fits to the asymmetric transits that we observe, we confirm that the transit egress is usually longer than the ingress, and that the transit duration is longer than expected for a solid body at these short periods, all suggesting that these objects have cometary tails streaming behind them. The precise orbital periods of the planetesimals are unclear, but at least one object, and likely more, have orbital periods of ~4.5 hr. We are otherwise unable to confirm the specific periods that have been reported, bringing into question the long-term stability of these periods. Our high-precision photometry also displays low-amplitude variations, suggesting that dusty material is consistently passing in front of the white dwarf, either from discarded material from these disintegrating planetesimals or from the detected dusty debris disk. We compare the transit depths in the V- and R-bands of our multiwavelength photometry, and find no significant difference; therefore, for likely compositions, the radius of single-size particles in the cometary tails streaming behind the planetesimals must be ~0.15 μm or larger, or ~0.06 μm or smaller, with 2σ confidence
Two 'b's in the Beehive: The Discovery of the First Hot Jupiters in an Open Cluster
We present the discovery of two giant planets orbiting stars in Praesepe
(also known as the Beehive Cluster). These are the first known hot Jupiters in
an open cluster and the only planets known to orbit Sun-like, main-sequence
stars in a cluster. The planets are detected from Doppler shifted radial
velocities; line bisector spans and activity indices show no correlation with
orbital phase, confirming the variations are caused by planetary companions.
Pr0201b orbits a V=10.52 late F dwarf with a period of 4.4264 +/- 0.0070 days
and has a minimum mass of 0.540 +/- 0.039 Mjup, and Pr0211b orbits a V=12.06
late G dwarf with a period of 2.1451 +/- 0.0012 days and has a minimum mass of
1.844 +/- 0.064 Mjup. The detection of 2 planets among 53 single members
surveyed establishes a lower limit on the hot Jupiter frequency of 3.8
(+5.0)(-2.4) % in this metal-rich open cluster. Given the precisely known age
of the cluster, this discovery also demonstrates that, in at least 2 cases,
giant planet migration occurred within 600 Myr after formation. As we endeavor
to learn more about the frequency and formation history of planets,
environments with well-determined properties -- such as open clusters like
Praesepe -- may provide essential clues to this end.Comment: 5 pages, 3 tables, 2 figures. Published in ApJ Letter
Two Small Planets Transiting HD 3167
We report the discovery of two super-Earth-sized planets transiting the
bright (V = 8.94, K = 7.07) nearby late G-dwarf HD 3167, using data collected
by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6 R_e and an
ultra-short orbital period of only 0.96 days. The outer planet, HD 3167 c, has
a radius of 2.9 R_e and orbits its host star every 29.85 days. At a distance of
just 45.8 +/- 2.2 pc, HD 3167 is one of the closest and brightest stars hosting
multiple transiting planets, making HD 3167 b and c well suited for follow-up
observations. The star is chromospherically inactive with low rotational
line-broadening, ideal for radial velocity observations to measure the planets'
masses. The outer planet is large enough that it likely has a thick gaseous
envelope which could be studied via transmission spectroscopy. Planets
transiting bright, nearby stars like HD 3167 are valuable objects to study
leading up to the launch of the James Webb Space Telescope.Comment: Accepted by ApJL. 6 pages, 1 figure, 2 table
Qatar Exoplanet Survey : Qatar-3b, Qatar-4b and Qatar-5b
We report the discovery of Qatar-3b, Qatar-4b, and Qatar-5b, three new
transiting planets identified by the Qatar Exoplanet Survey (QES). The three
planets belong to the hot Jupiter family, with orbital periods of
=2.50792 days, =1.80539 days, and =2.87923 days.
Follow-up spectroscopic observations reveal the masses of the planets to be
=4.31 , =6.10 , and
= 4.32 , while model fits to the transit light
curves yield radii of = 1.096 , =
1.135 , and = 1.107 . The
host stars are low-mass main sequence stars with masses and radii =
1.145 , = 0.896 ,
= 1.128 and = 1.272 ,
= 0.849 and = 1.076
for Qatar-3, 4 and 5 respectively. The V magnitudes of the three
host stars are =12.88, =13.60, and =12.82. All three
new planets can be classified as heavy hot Jupiters (M > 4 ).Comment: 13Pages, 8Figure
Multiwavelength Transit Observations of the Candidate Disintegrating Planetesimals Orbiting WD 1145+017
We present multiwavelength, multi-telescope, ground-based follow-up
photometry of the white dwarf WD 1145+017, that has recently been suggested to
be orbited by up to six or more, short-period, low-mass, disintegrating
planetesimals. We detect 9 significant dips in flux of between 10% and 30% of
the stellar flux from our ground-based photometry. We observe transits deeper
than 10% on average every ~3.6 hr in our photometry. This suggests that WD
1145+017 is indeed being orbited by multiple, short-period objects. Through
fits to the multiple asymmetric transits that we observe, we confirm that the
transit egress timescale is usually longer than the ingress timescale, and that
the transit duration is longer than expected for a solid body at these short
periods, all suggesting that these objects have cometary tails streaming behind
them. The precise orbital periods of the planetesimals in this system are
unclear from the transit-times, but at least one object, and likely more, have
orbital periods of ~4.5 hours. We are otherwise unable to confirm the specific
periods that have been reported, bringing into question the long-term stability
of these periods. Our high precision photometry also displays low amplitude
variations suggesting that dusty material is consistently passing in front of
the white dwarf, either from discarded material from these disintegrating
planetesimals or from the detected dusty debris disk. For the significant
transits we observe, we compare the transit depths in the V- and R-bands of our
multiwavelength photometry, and find no significant difference; therefore, for
likely compositions the radius of single-size particles in the cometary tails
streaming behind the planetesimals in this system must be ~0.15 microns or
larger, or ~0.06 microns or smaller, with 2-sigma confidence.Comment: 16 pages, 12 figures, submitted to ApJ on October 8th, 201
Asteroseismic properties of solar-type stars observed with the NASA K2 mission: results from Campaigns 1-3 and prospects for future observations
We present an asteroseismic analysis of 33 solar-type stars observed in short
cadence during Campaigns (C) 1-3 of the NASA K2 mission. We were able to
extract both average seismic parameters and individual mode frequencies for
stars with dominant frequencies up to ~3300{\mu}Hz, and we find that data for
some targets are good enough to allow for a measurement of the rotational
splitting. Modelling of the extracted parameters is performed by using
grid-based methods using average parameters and individual frequencies together
with spectroscopic parameters. For the target selection in C3, stars were
chosen as in C1 and C2 to cover a wide range in parameter space to better
understand the performance and noise characteristics. For C3 we still detected
oscillations in 73% of the observed stars that we proposed. Future K2 campaigns
hold great promise for the study of nearby clusters and the chemical evolution
and age-metallicity relation of nearby field stars in the solar neighbourhood.
We expect oscillations to be detected in ~388 short-cadence targets if the K2
mission continues until C18, which will greatly complement the ~500 detections
of solar-like oscillations made for short-cadence targets during the nominal
Kepler mission. For ~30-40 of these, including several members of the Hyades
open cluster, we furthermore expect that inference from interferometry should
be possible.Comment: 17 pages, 15 figures, 4 tables; accepted for publication in PAS
EPIC 220204960: A Quadruple Star System Containing Two Strongly Interacting Eclipsing Binaries
We present a strongly interacting quadruple system associated with the K2
target EPIC 220204960. The K2 target itself is a Kp = 12.7 magnitude star at
Teff ~ 6100 K which we designate as "B-N" (blue northerly image). The host of
the quadruple system, however, is a Kp = 17 magnitude star with a composite
M-star spectrum, which we designate as "R-S" (red southerly image). With a 3.2"
separation and similar radial velocities and photometric distances, 'B-N' is
likely physically associated with 'R-S', making this a quintuple system, but
that is incidental to our main claim of a strongly interacting quadruple system
in 'R-S'. The two binaries in 'R-S' have orbital periods of 13.27 d and 14.41
d, respectively, and each has an inclination angle of >89 degrees. From our
analysis of radial velocity measurements, and of the photometric lightcurve, we
conclude that all four stars are very similar with masses close to 0.4 Msun.
Both of the binaries exhibit significant ETVs where those of the primary and
secondary eclipses 'diverge' by 0.05 days over the course of the 80-day
observations. Via a systematic set of numerical simulations of quadruple
systems consisting of two interacting binaries, we conclude that the outer
orbital period is very likely to be between 300 and 500 days. If sufficient
time is devoted to RV studies of this faint target, the outer orbit should be
measurable within a year.Comment: 20 pages, 18 figures, 7 tables; accepted for publication in MNRA
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